Reactive oxygen species (ROS) have been implicated in teratogenesis. Responsive detoxification systems are paramount for embryonic protection and development. NRF2, a redox-sensitive transcription factor that binds to the ARE to upregulate phase II detoxification enzymes, may rely upon glutathione (GSH) and the oxidoreductase, thioredoxin (TRX1), for signal transduction, but this relationship is not completely defined. I propose to study the role of GSH/GSSG and TRX1 in NRF2 signal transduction. Due to the redox nature of both NRF2 activation and DNA binding, my hypothesis is that GSH/GSSG regulates NRF2 activation, while TRX1 regulates NRF2/DNA binding. I will test this hypothesis by chemical modification of GSH (oxidants, reductants, inhibitors) to change the GSH/GSSG ratios and concentrations to evaluate NRF2 activation and transfection of wild type and active site mutant forms of TRX1 engineered to contain both nuclear localization and nuclear export sequences to evaluate DNA binding. Co-transfection with an ARE4-Luc reporter will determine NRF2 activity. The roles of GSH and cytosolic and nuclear TRX during NRF2 activation and binding will provide an essential foundation for future developmental toxicology.